clearance?

[beppe180]

well i asked alot of ppl about the comp 260-h on my 92 3.1 , alot of ppl have it and run it with no problems. but i m guessing with stock pistons? anyway i have a set of camaro pistons in there, and the comp 260-h now since the dish on the piston top is smaller is its still gonna clear u think? any opinions, i can prob check but i didn;t get that far yet.. just wondering wut u guys think? thanks

Beppe

[dbtk2]

How much smaller is the dish on the camaro pistons? People run the 282 on stock pistons with no problems and it has .480 lift on the exhaust as opposed to the .454 of the 260. I can't imagine the pistons have that much less dish. The 260 is really a pretty small cam, it isn't much bigger than the stock one. I don't know from personal experience, but I sure can't see why it wouldn't fit.

Shawn

[beppe180]

hmm i dunno i was just curious i dont remember the exact size of the dish, but i was alittle concerned, how bout pushrods? which would b good replacments? or should i just use stock?

[beppe180]

i was looking at the comp pushrods # 7816-12 they said from 1980-86 or something but 60degree 173ci.. will they still work for a 92?

[dbtk2]

I believe those pushrods are for the iron head engine. I had the part numbers for the stock pushrods around here somewhere but I can't find them. I don't see any reason to get different pushrods, I'm using stock ones in my build.

Shawn

[v6h.o.]

you wont have any issues with the Camaro pistons.

the Dish on the pistons do not come into play with the "Canted" alum head valves.

the Valves will actually come in contact with the edge of the piston (just the suround around the dish)

there is no way the valve will have more clearance on the alum heads with any more or less dish the way they are possitioned. i know a few people running that camshaft (and larger) on the Iron headed 11:1 pistons in alum head engines.
you wont have any clearance issues.

and the pushrods your looking at are for the Iron heads as well.

[v6h.o.]

here is a pic of what i mean.

the red areas is where the valve will come incontact with the piston:

[beppe180]

ok it will come in contact. is it suppose to? is it safe? it wont break anything right?. ir ur sayin i wont have any issues.. it wont bend or break anything?

[sharkey]

no, its not safe. any metal to metal contact in a motor is very bad. if you got it running, it would bend every valve in the motor, and rip the pistons to shreads, but thats if you can get it to start.

[SappySE107]

However if you have the cam timed properly you wont have an issue unless the timing chain breaks. This is pretty much how it goes no matter what though so don't worry about it.

[v6h.o.]

ok it will come in contact. is it suppose to? is it safe? it wont break anything right?. ir ur sayin i wont have any issues.. it wont bend or break anything?

NO, it wont come in contact. but what i am showing in the picture is WHERE the valve will hit the piston IF there is contact. which the main point of my picture was to show that the Dish has no relevance as to if a valve has more or less piston to valve clearance on an Aluminum headed 660.

[beppe180]

ok thanks guys, just alil confused with the posts

[v6h.o.]

yeah no worries. you understand it all now?

[beppe180]

yea i do thanks alot.. u know the paranoia sets in when u have time to think about it LOL

[Corpse]

"they said from 1980-86 or something but 60degree 173ci.. will they still work for a 92?" - As was noted, the engines with Splayed and Siamesed valves (Gen I/II/III) have different length pushrods. Gen III: 6.074" Exhaust, 5.746" Intake. Gen II: 6.042" for the intake pushrod, 6.389" for the Exhaust. Gen I: 6.163"

Pushrods are very important in an engine as a worn or incorrectly made one could lose an end or collapse under high valve pressures. If you have a radical cam, you may want to defenitely upgrade the pushrods.

"wont have an issue unless the timing chain breaks." - Is the stock 2.8 HO cam (the one used for Gen II's) an Interference design or not? I've never checekd, if it is stock, then, either which way, stock or a crazy cam, if the chain breaks, it will be hurting. I like the thought of non-interference type designs, just because when the chain breaks, there are no worries but, you can't have such an aggressive cam profile.

"260-h now since the dish on the piston top is smaller is its still gonna clear " - You can be guaranteed that cam will be fine. one thing to remember in a motor with Splayed vales is, as lift/duration increases, and lobe seperation decreases, you also must worry about the valves colliding with each other. What is more to worry about is, you may have an engine that is very close on clearances and, if not properly used, and the motor displays even slight valve float from over-revving, you are screwed.

I think you may want to choose a more aggressive cam profile than a 260 though. Also, if you have added compression from those pistons, which you should, you may want to choose a cam that better suites the compression and general role of the motor.

-Dave